There has been known an arterial embolization technique for blocking nutrition by vascular blockage for malignant tumors and uterine fibroids incapable of removing surgically, in advance of incision in a surgical operation, in addition to purposes such as minimization of bleeding and hemorrhage prevention. Further, there has been known a chemical embolization process that blocks blood flow in a malignant tumor and expects the improvement of an anti-malignant tumor effect by keeping the concentration of an anti-malignant tumor medicine at a high level, by administrating the anti-malignant tumor medicine in combination with a blood vessel embolic material. As these embolic materials injected in the blood vessel, formulated particles of EVOH (DMSO solution with concentration of about 10%), cyano acrylate and polyvinyl alcohol (PVA) are known.
These embolic materials, for example, EVOH (a DMSO solution with a concentration of about 10%) has bad influences on the living body because the solvent DMSO solvent has toxicity. Cyano acrylate can control an embolization time in the blood by adjusting a mixing ratio with a hydrolyzed product of iodized fatty acid ester but the balance of the mixing ratio is difficult and when timing for extracting a catheter is mistaken after administration in the blood vessel through the catheter, the edge of the catheter adheres in the blood vessel and in the worst case, there is a fear that the edge of the catheter remains in the blood vessel. Further, the formulated particle of PVA is a permanent embolization material and there is a problem that it cannot be used for a temporary embolization use.
Various studies have been carried out for solving these problems. For example, in International Publication No. WO 98/03203, a gelatin sponge is used for temporary embolization, however, since a component derived from an organism is contained in the gelatin sponge, there is a fear that it mediates infection such as an AIDS virus. Further, when the gelatin sponge is used as a temporary embolic material, it is required to be very finely cut into a thickness of about 1 mm before use in order to pass the gelatin sponge through a catheter, and a very high degree of proficiency of a doctor is required. There is also a problem that there is a great difference in remedy effects between individuals. Further, although crosslinked starch is also generally used as the temporary embolic material, it is decomposed in minutes by amylase in the blood; therefore, it was not an embolic material that is effective for a comparatively long fixed period such as one week to 3 months.
Japanese Patent Unexamined Publication No. 2004-167229 discloses a blood vessel embolic material comprising a substantially granular particle having a water-swelling rate of at least 30% and degradability in phosphate buffered saline. However, the blood vessel embolic material is obtained by making a water-soluble polymer insoluble in water by methods such as block copolymerization by a biodegradable component, crosslinking and degradation, and since its degradation is caused by biodegradation, the control of the embolization time in the blood vessel was still inadequate.